Centurion 128-mpg ... and smaller engines

[sgtlethargic]

Originally Posted by Frank Lee

Optimization.

Gazuntite

[Ken Fry]

Originally Posted by sgtlethargic

How is the VW 1L prototype getting 170 mpg when 100 mpg seems like a stretch?

I'll second Frank's answer: optimization. It's a $400,000 economy car.

I'll add that part of the answer, however, lies in the website you referenced. Different test routines produce dramatically different mileage figures. The Riley is really a 70 mpg car (running through the EPA highway cycle) advertised as 128. The VW would not get 170 mph in an EPA test cycle. The X Prize results for the VLC are close to what the VLC would get in an EPA combined cycle (because the X Prize test was designed to be that way). They got something like 107 mpg, I think. The VW engine is probably more efficient as installed -- i.e. relative to the load. Total aero drag is lower, and if I recall, weight may be lower also. I would not be shocked at 135 - 150 mph EPA combined for the VW.

I may have mentioned this, but the Aptera with a 660cc kai engine (fuel injected gas) got 50 -55 mpg, almost all the time, according to Steve Fambro. Granted the Aptera is big, but it was very well-streamlined, and the small engine was at least pretty well-loaded. When you add a few sub-optimal choices here and a few more there, the overall efficiency can plummet.

In a plug in hybrid, like mine, there are lots of energy conversions. For the sake of simplicity, we'll say there are five processes. These can each be highly efficient: 95% .9^5 is 77%. They could each be OK: 80%: .8^5 is = 32% Big difference.

[Ken Fry]

Originally Posted by sgtlethargic

Gazuntite

Comes out loose?

[Ragnarok Warrior]

Originally Posted by Ken Fry

In a plug in hybrid, like mine, there are lots of energy conversions. For the sake of simplicity, we'll say there are five processes. These can each be highly efficient: 95% .9^5 is 77%. They could each be OK: 80%: .8^5 is = 32% Big difference.

And this is the biggest problem with any type of "hybrid". Be it gas, diesel, A/C, or D/C. In a Chevy Volt setup, where the engine only charges the battery pack, the engine can be run at its most efficient rpm and therefore the generator can be optimized to produce X voltage at Y amps at this rpm. This at current technology levels is probably the best solution. The problem lies in the conversion of energy from mechanical to electrical (and any other losses on the way).

Gasoline (or diesel) is a condensed form of energy of which we are only able to extract 35-45% of its stored energy from the combustion engine depending on engine/fuel used. Then you convert that mechanical motion into electricity via a generator, which would at most be ~60-70% efficient (the most efficient that I have read about). This electrical energy would be somehow transferred to an electric motor which can be from 80-95% efficient. So like Ken said, but using high and low numbers, you have .45*.70*.95=.29925 and .35*.60*.80=.168

BEFORE losses in transfer (as opposed to conversion) you have a power plant that would be from 17-30% efficient. Losses in mechanical conversions/transfers are usually greater than electrical which is why hybrids do offer some improvement on mileage, but you can see where improvements can be made.

[Ken Fry]

Originally Posted by Ragnarok Warrior

In a Chevy Volt setup, where the engine only charges the battery pack, the engine can be run at its most efficient rpm and therefore the generator can be optimized to produce X voltage at Y amps at this rpm. This at current technology levels is probably the best solution. The problem lies in the conversion of energy from mechanical to electrical (and any other losses on the way).

You have actually described the Zing setup (which is a strict series plugin hybrid) rather than the Volt setup which is a multi-mode hybrid that directly drives the wheels at times. The Volt architecture was changed (strangely to the chagrin of some EV enthusiasts) to improve the poor efficiency of the engine. Even with the 15% improvement gained by enabling direct-to-wheels drive at cruise speed, the gasoline-only fuel efficiency (37 mpg) is pretty poor if the benchmark is the Prius.

In the Zing, the engine either runs at full load or not at all, and driving force comes from the electric motor. Were it not for the hybridizing, the engine would vary in efficiency from 0% while idling to 5% at low load to 15% at moderate load, to 32% at full load, which would very rarely be used: there is no point in either the urban or highway drive sequence in which full power is required. The hybridizing allows for near doubling of fuel efficiency, despite the generator and motor losses (in my case each is 90% efficient). A bigger advantage, though, is that the fuel used most of the time is a small fraction of the price of gasoline -- and in most of the country is also cleaner from well to plug.

As you said the losses are large, but it is about the best we can do right now.










rid.

[Ragnarok Warrior]

Originally Posted by Ken Fry

As you said the losses are large, but it is about the best we can do right now.

Thats what I meant by "today's technology". I didn't realize that the Volt had switched to parallel drive. The one I drove last April was brought up by the GM reps and was only driven by the electric motor and charged by the gasser.

[Ken Fry]

Originally Posted by Ragnarok Warrior

Thats what I meant by "today's technology". I didn't realize that the Volt had switched to parallel drive. The one I drove last April was brought up by the GM reps and was only driven by the electric motor and charged by the gasser.

Every production Volt has the power split capability. GM came out with some statement about how they had not lied when they earlier had stated that the was no mechanical connection whatsoever between engine and wheels. But in fact the connection is like the Prius, where the power is split. You can say for the Prius that there is no direct connection, no single transmission shaft between engine and wheels, but you'd be stretching the truth... a lot.

It would be like lifting one wheel of a car with an open differential of the ground and applying power. "See... no movement. Therefore, there is no direct mechanical connection." Seems to me this is beyond a stretch of the truth.

But all the Volts, when at high speed and as required, power the wheels partially with the engine, via gearing.
Exclusive: Chevrolet Volt Chief Engineer Explains Volt Drivetrain, Says "Volt is an Electric Vehicle" | PluginCars.com
Motor Trend Explains the Volt’s Powertrain

From motor trend:
"Markus liked driving the car and he noted he was surprised about the direct mechanical connection."
GM flavors it this way so people have a harder time saying they lied: "GM says the engine never drives the wheels all by itself, but will participate in this particular situation in the name of efficiency,"

As you experienced, most people selling them had no idea there was this connection.

Another oddity I learned (?)** from a driver/promoter: the Volt does not charge up the battery when the engine is on. It simply keeps the battery at a low charge level***. This person was surprise when I told him that my Zing had gained charge on the way into Atlanta one day*. I guess that is what the "mountain" mode is about with the Volt. This if turned on before reaching mountains will increase the battery charge level, so you can climb the mountain without the performance falling off too much.

*This seems to me to be the way it should be, and actually, I'd have to make things more complicated if I wanted to avoid charging up the battery. Why on earth would I want to do that??

** I am not absolutely certain it is really this way -- but he's an electrical engineer and pretty convincing.

*** As I think about it, maybe this is one reason for the poor fuel efficiency. This would lead to a lot of short cycles, or a lot of time spent at less than full load -- neither on optimal.

[JackMcCornack]

Originally Posted by Ladogaboy

What do I personally think? Save your $95 and do free research online. That's money that could go toward actually buying yourself a Kubota diesel, a donor car, the tools to do a swap, etc.

Well at least you didn’t suggest getting a free pirate copy. ☺

Robert Q. Riley is a designer, not a manufacturer, and he makes his living selling plans. If your objective is to make one of his designs, the plans are a bargain. If you want to make a similar design, his plans are money well spent—I don’t have his Centurian plans, but I have other works of his, and they’ve been an inspiration.

If you want to make a car completely from scratch, his book Alternative Cars in the 21st Century: A New Personal Transportation Paradigm will save you days of dead ends. I paid $49 for my copy, off his web site page…
Alternative Cars in the 21st Century (2nd Edition)
…but you can get it cheaper from the SAE bookstore, particularly if you’re a member. I bought mine from him direct ‘cause that way he gets to keep more of the money. My copy is about worn out, I’m guessing it’s cost me a dollar an hour for time not wasted going down rabbit trails.

When doing your free research on line, I hope you’ll consider…

Automobile Ride, Handling, and Suspension
Three-Wheel Vehicle Handling Characteristics

PS-- RQ is very smart and he knows it. I hope we don’t get into trashing him on this forum, just because he Actually Does Things and/or he thinks his knowledge and effort are worth money and/or his writing style lacks warmth.

[Frank Lee]

I have the Centurion plans... got 'em back in the day, when they were brand new. I had a Spitfire then too, but for whatever reasons "my" Centurion didn't get built (IIRC I couldn't locate a reasonably priced diesel engine at that time- pre-internet shopping was sooo much harder!).

Another thing that really seems disingenuous today is the mileage claim at 35 mph... yes, it's ridiculous, but back then most fe claims were ridiculous. We had been gradually moving away from nonsense and towards usable fe estimates until, IMHO, they were quite good with the last generation of EPA tests, which have now gone downhill to reflect the stupidity of the average driver today.

[JackMcCornack]

Originally Posted by Frank Lee

Another thing that really seems disingenuous today is the mileage claim at 35 mph...

You've hit the nail on the head, Frank, it does seem disingenuous today.

Originally Posted by Ken Fry

The Riley figures are completely misleading, unless you read the fine print. Nobody else quotes mileage at 35 mph…By headlining 128 mpg, they are off to a bad start…The streamlining is awful…its "all show, no go."

For a bit of historical perspective, the prototype was built and those plans were offered 30 years ago, when the National Speed Limit was 55 mph. Riley's mileage figures are clear ("At 35 mph, Centurion delivers at 128 mpg. At 45-mph, fuel economy is 103 mpg, and at 55 mph it drops to 85 mpg.") and are in the body of the information of that page, they're sure not hidden away, and by the standards of the era they're pretty impressive.

The styling is a bit too yesterday's-car-of-the-future for my tastes, and Riley's more recent vehicles are much improved in the streamlining department. Auto styling is a compromise of many factors; one factor is streamlining, one is cost, and one is what the public will accept. Circa 1980 the acceptance bar was not where it is today. I'd call the Centurion streamlining dated rather than awful, and again, streamlining was less important at 55mph than today's speeds.

Or perhaps I'm defending my own work by proxy. I too quote my mpg at 20mph slower that the highest legal speed I've seen of late (75 in Wyoming, yet I've bragged about getting 100mpg at 55) and while I didn't personally write it, my own 127mpg result in the 2011 Mid-Ohio Vetter Fuel Mileage Challenge (100 miles of mixed environment, including a short 70mph blast on the freeway) made at least one headline, and you had to read the article to find we were mostly just gently cruising on rural roads and had perfect weather for a mileage competition.

I don't post much on ecomodder nowadays. Maybe I'm thin skinned, but it seems like the meanies have taken over the asylum and I don't want to paint a target on myself. It's getting kinda cliquish, and folks that don't fit the mold get trashed for doing their own thing. This Centurion forum started well, with a technical discussion of the Centurion, then it drifted to accusations of "shenanigans" that seemed more about writing style than content, and now it's about the Volt.

Ken, if you dispute Riley's claims for the car, I'd like to hear about it, and I'm sure so would others. Are his figures "completely misleading" because they're wrong? Ragnarok thinks they're wrong ("I would not believe the high mileage on the Centurion because of it's aero"), I think they're likely pretty accurate; it might make for an interesting discussion--we could all give reasons for our opinions. There's plenty to talk about re the Centurion (the OP made a good start) but for folks that don't like its presentation and would rather talk about plug-in hybrids, couldn't you start a fresh PIH or Volt thread instead of hijacking this one?